Fuel injectors are commonly used to pressure inject liquid fuel into the combustion cylinders of diesel engines. As is well known, fuel injectors include a pump in the form of a plunger and bushing or cylinder which is actuated, for example, by an engine driven cam. The pump is utilized to pressurize fuel to a suitable high pressure so as to effect the unseating of a pressure actuated injection valve in the fuel injection nozzle incorporated into the injector.
In one form of a common fuel injector, a solenoid valve is incorporated into the injector so as to control the drainage of fuel from the pump chamber of the unit injector. In this latter type of injector, fuel injection is controlled by the energization of the solenoid valve, as desired, during a pump stroke of the plunger, thereby terminating drain flow and permitting the plunger to increase the fuel pressure to effect unseating of the injection valve of the associated fuel injection nozzle. An example of such an electromagnetic fuel injector is disclosed in U.S. Pat. No. 4,129,253 entitled "Electromagnetic Fuel Injector"]issued Dec. 12, 1978 to Ernest Bader, Jr., John I. Deckard and Dan B. Kuiper, and assigned to the assignee of the present invention.
Another example of the electromagnetic fuel injector is disclosed in U.S. Pat. No. 4,392,612 entitled "Electromagnetic Fuel Injector" issued Jul. 12, 1983 to John I. Deckard and Robert D. Straub, also assigned to the assignee of the present invention. These prior art fuel injectors include what is known in the industry as a sac-type injector tip or nozzle, meaning that there is a free space or cavity between the end of the injection valve and the bottom of the injector tip. In the patents mentioned, the spray orifices are located in the sac and thus below the valve seat. It is also common to locate the spray orifice radially apart the valve seat; thus being referred to as a valve covered orifice (VCO) type injector tip. Other injection fuel tip designs exist but are not in use to the extent of those mentioned.
In all cases, the objective is to acquire an effective fuel spray to the combustion chamber, e.g., a complete and quick dispersion of fuel to all areas of the combustion chamber for efficient combustion. Likewise, an objective is to provide a nozzle tip design which is minimally effected by a production of combustion product deposits, i.e., hydrocarbon deposits, which effect the metering or passage of fuel through the spray orifices.